Automatically releasing lifting tongs



Aug 28, 1962 E. A. sKowRoN 3,051,521

AUTOMATICALLY RELEASING LIFTING TONGS Filed Feb. 9, 1962 2 Sheets-Sheet l INVENTOR. EDMU/VA/UWQO/V Aug. 28, 1962 E. A. sKowRoN AUTOMATICALLY RELEASING LIFTING TONGS Filed Feb. 9, 1962 2 Sheets-Sheet 2 United States Patent O 3,051,521 AUTOMATICALLY RELEASING LE'HNG TNGS Edmund A. Skov/ron, Verona, la., assigner to Woodngs- Verona Tool Works, Verona, Pa., a corporation of Pennsylvania Filed Feb. 9, 1962, Ser. No. 172,318 3 Claims. (Cl. 294-83) This invention relates to tongs for lifting heavy loads, and more particularly to those used with cranes and the like.

In transporting articles from one location to another in a manufacturing plant it is not uncommon to use tongs that are suspended from overhead cranes. Sometimes the tongs are designed to lift a single article, while at other times they are intended for lifting bags containing a large number of small objects. Heretofore, it has been -necessary to employ a man to attach the tongs to the load that is to be lifted, and another man to release the load at its destination unless the iirst man follows the tongs back and forth.

lt is among the objects of this invention to provide lifting tongs which are of 'relatively simple construction, which release themselves automatically from -a load when it is lowered onto a support, and which remain in released position until clamped onto the next load.

ln accordance with this invention a vertical handle is provided at its upper end with means for suspending it from a crane or the like, and is provided at its lower end with an upwardly extending slot that extends laterally through it. Extending across the lower part of the slot is a cross pin, on which the upper ends of a pair of inclined upper toggle links are pivotally mounted. The links extend laterally out of the opposite sides of the slot and down. A crossed pair of lower toggle links have their crossed portions pivotally connected by a center pin, while end pins pivotally connect ltheir upper ends to the lower ends of the upper links. Clamping members are secured to the lower ends of the lower links.

Disposed in the handle at opposite sides of its slot and extending down below it is a pair of vertical bars that have their lower ends mounted on the opposite ends of the `center pin. The bars have vertical slots that receive the cross pin so that they can slide vertically in the handle. Connected with the bars below the cross pin is a stop member that has downwardly facing surfaces. Releasable means connected to the upper llinks extend down under the stop member surfaces while the stop member is in its upper position. The releasable means normally hold the stop member in its upper position to space the clamping members apart. The latter are clamped onto the yarticle that is to be lifted by simply pressing them together, which causes the stop member to move down away from the releasable means. As soon as the handle is lifted, the action of the toggle causes the clamping members to tightly grip the load between them. When the load is set down, the handle is lowered and its weight pushes the cross pin down relative to the center pin until the releasable means once again extend down under the stop member surfaces and hold that member in raised position, with the clamping members spaced apart, when the tongs are lifted.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. l is a face view of the tongs while open;

FG. 2 is a side view thereof;

FIG. 3 is a horizontal section taken on the line lll- III of FIG. l;

FIG. 4 is a horizontal section taken on the line IV-IV of FIG. 2;

FIG. 5 is a view similar to FIG, l, but showing the tongs lifting a load; and

3,5L5Zl Patented Aug. 28, 1962 ice FIG. 6 is a vertical `section taken on the line Vl-VI of FIG. 5.

Referring to the drawings, a rather long rigid handle l, which for best results is a heavy metal bar, is provided at its upper end with a rigid loop 2, by which it can be suspended from the hook 3 of a crane (not shown). The connection between the hook and loop is such that the handle will not be released from the hook accidentally. The lower end of the handle is provided with a slot 4 that extends through it from one side -to the other and also upwardly into it for several inches. A cross pin 5 extends through the lower end `of the handle and across the slot near its lower end. This pin pivotally carries the upper ends of ya pair of upper toggle links 6. The links extend `out through the sides of the slot and are inclined downward. Their lower ends are connected by end pins 7 to the upper ends of another pair of toggle links S. These lower links cross each other and are pivotally connected together at the crossing point by a center pin 9. The lower ends of the lower links are curved downwardly and support opposed clamping members l0 in the form of plates, generally having ribbed or knurled inner faces.

Also disposed in the handle at the opposite sides of its slot is a pair of vertical bars l2 that extend down below the handle and have their lower ends mounted on the opposite ends of center pin 9. The ba-rs are provided with vertical slots 13, through which cross pin 5 extends so that the bars can move up `and down in the handle. Preferably the bars are connected to the handle and guided in their vertical movements by providing the opposite side walls of the slot with upwardly extending grooves 14, in which Athe bars slide. lt will be seen that when the clamping plates are in their upper spread-apart position (FIG. l) the bars `are raised, and when the plates are swung together (FIG. 5) the bars are lowered.

When the tongs are lifted with a load between the clamping plates, the toggle action of the links tends to close the lower links still further and cause the plates to grip the load tightly. When the load is set down on a support and the tongs are lowered still further, downward movement of the clamping plates and bars l2 will be stopped sooner or later but the continued downward movement of the handle and cross pin 5 will cause the handle to slide down on the bars so that the cross pin will approach the center pin 9. This action will spread the lower links S farther apart and thereby cause the clamping plates to be released lfrom the load. When the cross pin reaches the lower ends of the slots 13 in the bars, there can be no further opening of the links. lt will be seen that if the tongs as described -thus far were now lifted again, the clamping plates would close together and have to be pulled apart by a workman before they could be attached to the next load. To avoid that, a feature of this invention is to automatically maintain the clamping plates spread apart after they have released a load until `manually applied to the next load.

Accordingly, la stop member is connected with bars 12 below the cross pin and has downwardly facing surfaces engageaole by releasable means when it is in its upper position. The stop memlber may take the form of a block lo disposed between the bars in the area between the upper and lower toggle links. The block may be rigidly secured to both bars. The releasa'ble means may take the form of latch levers 17, the central portions of which are connected by pivot pins 18 to the central portions of upper links 6. When the stop block is in its upper position as shown in FIG. l, the lower ends of the levers extend beneath its downwardly facing surfaces, which may be at its bottom. The levers are held in that position by springs, or by ounterweights 19 mounted on their upper ends. When it is desired to clamp onto a load, for example a bag 2l? of metal forgings as shown in FIG. 5, the clamping plates 1G are merely pushed toward each other manually which will tbe suflicient to overcome the resistance ofthe counterweights and thereby cause the stop block to slide downward between the lower ends of levers 17. On the other hand, when the handle is moved downward relative to the bag to Vrelease the load, the lower ends of the latch levers slide down the opposite sides of block 16 until they can swing in beneath its bottom to hold i=t up when the tongs are raised again. The tongs therefore are returned to the loading area in the wide open condition shown in FIG. l, ready to be closed onto the next load. No one is required for disconnecting the tongs from the load nor for opening them for application to the next load.

According to the provisions of the patent statutes, I have explained the iprinciple of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope `of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. Automatically releasing lifting tongs comprising a vertical handle provided at its :lower end with an upwardly extending slot through it, a cross pin extending across the lower part of the slot, a pair of inclined upper toggle links having upper ends pivotally mounted on said pin and extending laterally out of opposite sides of the slot and down, `a crossed pair'of lower toggle links, a center pin pivotally connecting the crossed portions of the lower links, end pins pivotally yconnecting the upper ends of the lower links to the lower ends of the upper links, clamping members secured to the lower ends of the lower links, a pair or" vertical bars disposed in the handle at opposite sides of said slot and extending down below the handle with their lower ends mounted on the opposite ends yof said center pin, the fbars havingy vertical slots receiving said cross pin to permit vertical sliding of the bars in 'the,handle, -a stop member secured 'between the bars in the area between the upper and lower links, the stop member having downwardly facing surfaces, holding levers pivotally connected to the upper links and extending down and under said stop member surfaces while the stop member is in its upper position, and means connected to said levers urging their lower ends up yagainst lthe stop member to normally hold said bars in said upper position to space said clamping members apart, said lower ends of the holding levers being swingable down away from said stop member surfaces by the pressure of the stop member against them when said clamping memlbers are pressed toward each other manually.

2. Automatically releasing lifting tongs comprising a vertical handle provided at its lower end with an upwardly extending slot through it, a cross pin extending across the lower part of the slot, a pair of inclined upper toggle links having upper ends pivotally mounted on said pin and emending laterally out of opposite sides of the slot and down, a crossed pair of lower toggle links, a center pin pivotally connecting the crossed portions of the lower links, end pins pivotally connecting the upper ends of the lower links to the lower ends of the upper links, clamping members secured to the lower ends of the lower links, the side walls of said handle slot being provided with straight grooves extending upward from the lower end of the handle, `a pair of vertical bars slidably mounted in said grooves and extending below the handle with their lower ends mounted on the opposite ends of said center pin, the bars being spaced apart by said links and having vertical slots through which said cross pin extends, a stop member secured between the fbars in the area between the upper and lower links, the stop member having downwardly facing surfaces, holding levers pivotally connected to the upper links and extending down and under said stop member surfaces while it is in its upper position, land means connected to said levers urging Itheir lower ends up against the stop member to normally hold said bars in said upper position with said clamping members spaced apart.

3. Automatically releasing lifting tongs comprising a vertical handle provided at its lower end with an upwardly extending slot through it, a cross pin extending across the lower part of the slot, a pair of inclined upper toggle links having upper ends pivotally mounted on said pin and extending laterally out of opposite sides of the slot and down, a crossed pair `of lower toggle links, a center pin pivot-ally `connecting the crossed portions of the lower links, end pins pivotally connecting the upper ends of the lower links to the lower ends of the upper links, clamping members secured to the lower ends of the lower links, the side walls of said handle slot being provided with straight grooves extending upward from the lower end of the handle, a pair of vertical bars slidably mounted in said grooves and extending below the handle with their lower ends mounted on the opposite ends of said center pin, the bars being spaced apart by said links and having vertical slots through which said cross pin extends, a stop member secured between the bars in the area between the upper and lower links, holding levers pivotally connected to the upper links and extending `down and under said stop 'member while it is in its upper position, and counterweights mounted on the upper ends of said levers urging their lower ends up against the stop member to normally hold said bars in said upper position with said clamping memfbers spaced apart.

References Cited in the tile of this patent FOREIGN PATENTS 152,192 Great Britain of 1920 

